1. Field of the Invention
The present invention relates to split engines, in which the average number of cylinders supplied with fuel is selected in accordance with different operating conditions. More specifically, the present invention relates to a fuel injected engine where specific injectors are deactivated to permit the engine to run on less than all its cylinders in a balanced manner.
2. Description of the Related Art
It is well known in the art that their are numerous benefits to operating an engine with less than a full complement of cylinders under certain loads and running conditions. Thus, it is possible to increase fuel economy and decrease exhaust emissions and engine wear by running an engine on a reduced number of cylinders when operating a vehicle under light loads. However, prior art techniques for implementing a split engine apparatus have had numerous drawbacks, hindering the commercial use of split engine technology. Typically, in an eight cylinder engine using current split engine technology, four cylinder mode operation is achieved by simply deactivating four cylinders, while six cylinder mode operation is achieved by deactivating two cylinders. This elementary implementation of split engine technology results in an engine that operates roughly, in an unbalanced manner, when operating with less than a full complement of cylinders. Another limitation to traditional split engine technology is that when an engine is operated with less than its full complement of cylinders, the same cylinders are repeatedly idled. This results in uneven wear of the cylinders and related hardware.
A further drawback to traditional split engine implementations is that a new split engine control unit is required to replace the non-split engine controller. This limitation requires that the split engine controller be installed by the car manufacturing as a "stock" controller, due to the extent of re-wiring and mechanical installation needed for the split engine controller. Thus, it would be expensive and impractical for a car owner to upgrade her car engine to split engine operation.
Yet another limitation to traditional split engine implementations is that the cylinder itself is deactivated so that no air flows through the deactivated cylinders. This results in higher percentage concentrations of pollutants in the engine exhaust than would be present if air continued to flow through the deactivated cylinder.
Therefore it would be desirable to have a split engine system which operated smoothly with less than a full complement of cylinders and which switched operating modes.